Container having collapsible liner

ABSTRACT

A composite container is provided for vacuum packaging of products is disclosed having a generally tubular body portion having opposite ends and an inner surface. A liner is attached to the body portion for receiving the products inside the liner and the body portion of the container. The liner has a memory and is able to move between a position adjacent the body portion to a position about the products placed therein when a vacuum is applied to the products. When the vacuum is removed from the products, the liner automatically returns from the position about the products to the position adjacent the body portion so that the products can be easily removed.

FIELD OF THE INVENTION

[0001] The present invention relates to containers for packaging products and, more particularly, composite containers for vacuum packaging of products having a liner for automatically constricting and moving away from a container body portion when a vacuum is applied, and then contracting and moving back toward the body portion when the vacuum is released.

BACKGROUND OF THE INVENTION

[0002] Composite containers have been utilized in lieu of metal, plastic or glass containers in many instances for packaging of various products, including food products, due to their cost efficiencies, etc. A typical composite container includes a generally tubular body portion made from paperboard, a liner ply attached to the inner surface of the body portion made from a paper-backed foil that is generally impervious to liquid transmission, a label ply attached to the outer surface of the body portion, and a pair of end closures. In some cases, these containers are packaged with an internal vacuum, but problems can arise when the body portion of the composite container lacks adequate strength to maintain its shape after a vacuum is created inside the container, which can cause the container to collapse inwardly.

[0003] In an effort to overcome this problem, a loose liner system has been utilized in some composite containers, as disclosed in U.S. Pat. No. 4,158,425, assigned to the assignee of the present invention, the disclosure of which is incorporated herein by reference. As may be seen in this U.S. patent, the relatively slack liner of the composite container is secured solely at the opposite ends thereof. As a result, the liner is pulled inwardly toward the product when a vacuum is created inside the container. This provides a solution to the problem of a collapsing body portion, as the wall of the body portion has no inwardly directed forces at an intermediate portion thereof. In addition, the body portion may be relatively porous so as to allow the pressure differential across it to equalize over time, particularly if a vent hole is utilized.

[0004] However, this composite container with a loose liner system produces additional problems. When the container is opened and the vacuum is released, the liner stays pulled against the product. This causes the volume available for the product within the container to remain reduced and does not allow the product to settle back into the container. As a result, the product tends to create a bottleneck near the opening of the container so that it is difficult to remove without spillage. The product can also be pressed against the liner and the end closures when under vacuum and therefore can be broken or damaged during the vacuum packaging process. This is particularly disadvantageous when packaging fragile products, such as potato crisps or cookies, as broken products are wasteful and aesthetically displeasing to the consumer. Also, the liner inside of the container looks baggy or loose when the product is removed, providing a bad impression to the consumer.

[0005] To address such problems, composite containers have been developed having a retractable liner as disclosed in U.S. Pat. No. 5,988,493, which is also assigned to the assignee of the present invention, the disclosure of which is incorporated herein by reference. The '493 patent is directed to a composite container having a body portion and a liner that are separated by an elastic material that adheres to the liner and to the inner surface of the body portion. The elastic material, which can be applied in a pattern or as a solid coat, is capable of stretching as a vacuum is applied to products contained within the liner such that the liner constricts about the products for support and protection against breakage and the like. When the vacuum is released, the elastic material retracts, which helps pull the liner away from the products. However, the elastic material disposed between the body portion and the liner occupies space, which effectively reduces the volume available for the products. In addition, the elastic material can be relatively slow to retract when the vacuum is removed from the products, which can make removing the products difficult. Further, the elastic material adds cost and complexity to the manufacturing process. Thus, while the container of the '493 patent provides significant advances in the state of the art, further advances are desirable.

SUMMARY OF THE INVENTION

[0006] It is the object of this invention to provide a container for vacuum packaging of products which utilizes a liner that can constrict inwardly from the body portion of the container when a vacuum is created in the container, yet retract automatically when the vacuum is removed. As such, additional elastic material is not required, and the liner of the present invention retracts significantly faster than the liner disclosed in the '493 patent or in conventional liners.

[0007] In particular, a container for vacuum packaging a product according to one embodiment of the present invention includes a generally tubular body portion, such as a paperboard tube or the like, having opposite ends and an inner surface. Preferably, the body portion of the container is formed by spirally winding paperboard strips to form a generally cylindrical shape. End closures are preferably positioned on open ends of the body portion for hermetically closing the container.

[0008] A generally tubular liner is also provided. The liner is formed of a resiliently stretchable, flexible material that is substantially impervious to fluids. The liner is disposed within the body portion and has opposite ends that are attached to the body portion, such as with a dextrine adhesive, and an unattached medial portion that can constrict and move away from the body portion when a vacuum is applied. Advantageously, the liner has a memory such that the medial portion of the liner retracts to an initial position when the vacuum is released. In one embodiment, the liner comprises an oriented polymeric film, and more particularly a metallized, oriented polymeric film. Examples of such materials are metallized oriented polyethylene terepthalate, metallized oriented polypropylene, metallized biaxially oriented nylon, and equivalents thereof. The liner according to one embodiment of the present invention is formed of a material having a modulus of elasticity between about 450,000 psi and about 650,000 psi and an ultimate elongation of between about 75% and about 200%. As such, the liner retracts relatively quickly when the container is opened and the vacuum is released, which allows the products to be easily removed from the container.

[0009] The liner of the present invention has a first position adjacent the body portion of the container. When a vacuum is applied to the container, the unattached medial portion of the liner is free to move inwardly toward the products to a second position so as to secure and protect the products. A vent hole is defined in the body portion so that the pressure between the body portion and liner is equalized with ambient pressure. When the container is opened and the vacuum is released, the memory in the liner causes the liner to retract to the first position adjacent the body portion. In one embodiment, a plurality of fragile products are arranged between the opposite ends of the body portion of the container. Due to the advantages of the present invention, the liner of the present invention can move between the first and second positions without breaking or damaging the fragile products proximate the opposite ends of the body portion, yet retract quickly so that the products can be removed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0011]FIG. 1 is a perspective view of a container according to one embodiment of the present invention with a portion broken away for clarification purposes;

[0012]FIG. 2 is cross-sectional view of the container shown in FIG. 1 illustrating the container liner constricted about the products placed therein while a vacuum is applied;

[0013]FIG. 3 is a close-up cross-sectional view of a portion of the container as indicated in FIG. 2; and

[0014]FIG. 4 is cross-sectional view of a container according to one embodiment of the present invention illustrating the container liner moved back into a position adjacent the body portion after the vacuum is removed.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

[0016] Referring to FIGS. 1-4, a composite container generally indicated at 10 and constructed in accordance with this invention for vacuum packaging of products P is illustrated. The container 10 comprises a generally tubular body portion 12 defining a desired shape for the container 10 and having an inner surface 13. The body portion 12 of the container 10 is preferably formed by spirally winding paperboard strips to define a generally cylindrical shape for the container. The body portion 12 serves to resist radial and axial crushing of the container, including when the container 10 is subjected to a vacuum. An outside label layer 14 may be utilized and preferably is spirally wound on an outer surface of the body portion 12 in a manner well understood by those with ordinary skill in the art.

[0017] The body portion 12 may be formed by spirally winding one or more plies of paperboard or board stock to form a tube whose wall has a radial thickness of between about 0.100 and about 0.35 inch, preferably between about 0.105 and about 0.30 inch, for example, about 0.21 inch. Board stock conventionally used in the manufacture of spirally wound composite containers is commercially available from various manufacturers including Sonoco Products Company, Republic Paperboard Corporation and Middletown Board Corporation. In order to function advantageously as the spirally wound paperboard hollow body portion, the board stock typically is composed of kraft or recycled paper and can typically range from about 50 to about 100 lbs./ream. In some instances, the wall of the body portion 12 can include a weak exterior layer (not shown), e.g. a 0.003 inch exterior news. In the illustrated embodiment, the body portion 12 is comprised of two more paperboard layers 12A and 12B wound on top of the other and adhered together with a suitable adhesive. The label layer 14 is conventionally constructed from suitable materials, such as kraft paper, a polymer/foil laminate, a kraft paper/foil laminate, or the like. In addition, a vent 32, which can be in the form of a hole, slit, or other shape, is formed through both the body portion 12 and the label layer 14 so that air outside the container 10 can enter through the vent 32 into a space 16 inside the body portion 12 when the vacuum is applied to the products P.

[0018] The container 10 also includes end closures 20 on each open end of the hollow body portion 12 for hermetically closing the hollow body portion 12. The end closures 20 may be double-seamed with the open end portions of the hollow body portion 12 in a manner well understood by those with ordinary skill in the art. The bottom end closure 20 may typically be constructed of steel or aluminum plate with applied coatings and/or electrolytic tinplate. Top closure 20 may be of a steel or aluminum plate with applied coatings and/or electrolytic tinplate with a center panel of a flexible laminate made of films, foil, and/or extruded polymers, or it may be made totally of a flexible laminate made of films, foil, and/or extruded polymers heatsealed or adhesively attached to the container body.

[0019] A generally tubular liner 30 is positioned within the hollow body portion 12. The liner 30 is formed of a resiliently stretchable, flexible material that is substantially impervious to fluids, as discussed below. The liner 30 has opposite ends corresponding to the opposite ends of the body portion 12 that are attached thereto with a suitable adhesive, such as a dextrine adhesive. Alternatively, other adhesives could be used, such as polyvinyl acetate, polyvinyl acetate copolymers, including but not limited to polyethylene vinyl acetate, or polyacrylics, including but not limited to acrylic copolymers. In one embodiment, the opposite ends of the liner 30 are attached to the body portion 12 with about a ½″ band of dextrine adhesive, which may be a solid strip or may be in a patterned configuration. The band of adhesive may be greater or less than ½″ depending on several factors including the length of the container, the amount of vacuum applied, the type of adhesive used, and the type of liner material used. By attaching the opposite ends of the liner 30 to the body portion 12, the liner therefore includes an unconnected medial or interior portion between the opposite ends of the liner that defines part of the space 16 between the medial portion of the liner and the inner surface 13 of the body portion 12. The medial portion of the liner 30 is free to be constricted inwardly away from the body portion when a vacuum is applied. Advantageously, the liner 30 has a memory such that the liner will contract and move back to an initial position adjacent the inner surface 13 of the body portion 12 if the container is opened and the vacuum is released.

[0020] Advantageously, the liner 30 is a resiliently stretchable, flexible barrier type material, such as an oriented polymeric film. The liner 30 preferably has a modulus of elasticity of between about 450,0000 psi and about 650,000 psi, and more particularly about 600,000 psi, and an ultimate elongation of between about 75% and about 200%, and more particularly about 100%. The liner 30 also is an oxygen or gas barrier so that the vacuum process is effective. In this regard, the liner 30 has a maximum gas transmission rate of about 0.10 cc/100 in²/24 hours, and preferably has a maximum gas transmission rate of about 0.04 cc/100 in²/24 hours. Suitable examples of such materials are metallized oriented polyethylene terepthalate (MOPET), which is available from E. I. du Pont de Nemours and Company; metallized oriented polypropylene (MOPP), which is available from Exxon Mobil Corporation; and metallized biaxially oriented nylon (MBON), which is available from Honeywell Corporation. The liner 30 can be a multi-layer polymer film structure having layers of different polymer materials laminated or co-extruded together. For example, the liner 30 can have the structure: natural kraft/low-density polyethylene (LDPE)/MOPET/high-density polyethylene (HDPE). The kraft layer goes against the inner surface 13 of the body portion 12 and facilitates adhering the liner to the body wall.

[0021] In accordance with this invention, the liner 30, and more specifically the medial portion of the liner, is capable of moving between a first position, which preferably is adjacent the inner surface 13 of the body portion as shown in FIGS. 3 and 4, and a second position, which is preferably around or about a product or products P that are placed therein as shown in FIG. 2. In particular, the medial portion of the liner 30 constricts and moves away from the body portion 12 when a vacuum, such as about 5-15 in. Hg, and more particularly about 12.5 in. Hg, is applied to the product positioned in the container 10 (as illustrated in FIG. 2). The liner 30 is stretched by the vacuum. When the container is opened and the vacuum is released, the liner 30 moves back relatively quickly to the first position adjacent the inner surface 13 of the body portion 12 (as shown in FIG. 4). And as described above, the vent 32 allows the pressure inside and outside the body portion 12 to equalize so that the body portion is not substantially deformed by the vacuum packaging process. Advantageously, the container of the present invention avoids the problems discussed above with respect to the previous loose liner systems in vacuum packaged composite containers of U.S. Pat. Nos. 4,158,425 and 5,988,493.

[0022] The container of the present invention is particularly advantageous for packaging fragile products, such as a plurality of potato crisps or cookie biscuits, that can be easily damaged during the vacuum packaging process. In particular, the liner 30 is able to constrict enough to protect and support the fragile products inside the container including the products nearest the opposite ends of the container that are the first to be seen by the consumer when the container is opened, yet retracts quickly when the vacuum is removed such that the products can be easily removed. The degree to which the liner constricts radially inwardly depends on the amount of vacuum applied, the elastic modulus of the liner 30, and other factors. Advantageously, the liner 30 is configured and the vacuum is applied such that the products are not broken by the liner 30 moving between the first position adjacent the body portion 12 and the second position about the products P, and the products are not difficult to retrieve when the vacuum is removed.

[0023] By this invention, a composite container 10 for vacuum packaging of products P is provided that includes a liner 30 arranged to constrict and move away from the body portion 12 when a vacuum is formed on the products P packaged in the container 10 and to automatically contract and move back to an initial position adjacent the body portion 12 of the container 10 when the container is opened and the vacuum on the products is removed. This construction overcomes the prior problems with composite containers for vacuum packaging of products, and provides secure protection for the products while not damaging the products during the vacuum process.

[0024] Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 

That which is claimed:
 1. A container for vacuum packaging products, comprising: a generally tubular body portion having opposite ends and an inner surface; and a generally tubular liner of resiliently stretchable, flexible material that is substantially impervious to fluids, the liner being disposed inside the body portion and having opposite ends that are attached to the body portion and an unattached medial portion between the opposite ends, the liner being arranged to be stretched and constricted inwardly away from the body portion when a vacuum is applied such that the medial portion of the liner moves inwardly about a product placed inside the liner, whereby when the vacuum is released, the medial portion of the liner contracts and moves back outwardly to a position adjacent the body portion.
 2. A container according to claim 1, wherein the liner has substantially no slack when the liner is in the position adjacent the body portion, and wherein the liner is stretched by the vacuum.
 3. A container according to claim 1, wherein the liner comprises an oriented polymeric film having a memory.
 4. A container according to claim 1, wherein the liner comprises an oriented polymeric film selected from the group consisting of metallized oriented polyethylene terepthalate, metallized oriented polypropylene, and metallized biaxially oriented nylon.
 5. A container according to claim 1, wherein the liner has a modulus of elasticity between about 450,000 psi and about 650,000 psi.
 6. A container according to claim 1, wherein the liner has an ultimate elongation of between about 75% and about 200%.
 7. A container according to claim 1, wherein the liner has a modulus of elasticity between about 450,000 psi and about 650,000 psi and an ultimate elongation of between about 75% and about 200%.
 8. A container according to claim 1, wherein the liner has a maximum gas transmission rate of about 0.10 cc/100 in²/24 hours.
 9. A container according to claim 8, wherein the liner has a maximum gas transmission rate of about 0.04 cc/100 in²/24 hours.
 10. A container according to claim 1, further comprising a label affixed to an outer surface of the body portion.
 11. A container according to claim 1, wherein the liner is attached to the body portion with a dextrine adhesive.
 12. A container for vacuum packaging products, comprising: a generally tubular body portion having opposite ends and an inner surface; and a generally tubular liner of resiliently stretchable, flexible material that has a memory and is substantially impervious to fluids, the liner being disposed inside the body portion and having opposite ends that are attached to the body portion and an unattached medial portion between the opposite ends; an end closure on each of the opposite ends of said body portion for hermetically closing said body portion and said liner; and at least one product disposed inside said liner and said body portion, the liner being arranged to be stretched and constricted inwardly away from the body portion when a vacuum is applied such that the medial portion of the liner moves inwardly about a product placed inside the liner, whereby when the vacuum is released, the medial portion of the liner automatically contracts and moves back outwardly to a position adjacent the body portion
 13. A container according to claim 12, wherein the liner has substantially no slack when the liner is in the position adjacent the body portion, and wherein the liner is stretched by the vacuum.
 14. A container according to claim 12, wherein the liner is attached to the body portion with a dextrine adhesive.
 15. A container according to claim 12, wherein the liner comprises an oriented polymeric film selected from the group consisting of metallized oriented polyethylene terepthalate, metallized oriented polypropylene, and metallized biaxially oriented nylon.
 16. A container according to claim 12, wherein the liner has a modulus of elasticity between about 450,000 psi and about 650,000 psi.
 17. A container according to claim 12, wherein the liner has an ultimate elongation of between about 75% and about 200%.
 18. A container according to claim 12, wherein the liner has a modulus of elasticity between about 450,000 psi and about 650,000 psi and an ultimate elongation of between about 75% and about 200%.
 19. A container according to claim 12, wherein the liner has a maximum gas transmission rate of about 0.10 cc/100 in²/24 hours.
 20. A container according to claim 19, wherein the liner has a maximum gas transmission rate of about 0.04 cc/100 in²/24 hours.
 21. A container according to claim 12, further comprising a label affixed to an outer surface of the body portion.
 22. A container according to claim 12, wherein said at least one product comprises an plurality of fragile products arranged between the opposite ends of the body portion of the container, whereby the liner moves inwardly about the fragile products when the vacuum is applied without damaging or breaking the fragile products located proximate the opposite ends of the body portion. 